Komatsu PC750-7 Fault Code E95A: Complete Diagnostic Guide

What is Komatsu PC750-7 Fault Code E95A?

Fault Code E95A indicates a malfunction in the engine control system's communication circuit, specifically related to the CAN (Controller Area Network) bus communication error between the engine controller (ECM) and the monitor controller.

This code triggers when the Engine Control Module (ECM) detects abnormal or interrupted data transmission on the CAN communication line. The CAN bus is critical for the PC750-7's integrated control system, allowing real-time data exchange between the engine management system, hydraulic controllers, and operator display. When this communication fails, the machine cannot properly coordinate engine performance with hydraulic demands, potentially causing operational inefficiencies and safety concerns.

Common Symptoms

When Code E95A is active, operators typically experience:

• Warning light illumination on the monitor panel, often accompanied by a communication error message
• Intermittent or complete loss of engine parameter displays (RPM, coolant temperature, fuel level)
• Reduced engine power or derate mode activation as a protective measure
• Erratic hydraulic response due to improper engine-hydraulic system coordination
• Inability to access diagnostic information through the standard monitor interface

Potential Causes

The most common technical causes for E95A on used PC750-7 excavators include:

• Damaged or corroded CAN bus wiring harness, particularly at flex points near the engine mounting or cab pivot areas
• Loose or corroded connector pins at the ECM or monitor controller connection points
• Failed termination resistors on the CAN bus network (typically 120-ohm resistors at each end)
• ECM or monitor controller internal failure, though less common than wiring issues
• Voltage supply problems to either controller, causing communication dropout
• Water intrusion into harness connectors, common in machines with compromised sealing

How to Troubleshoot and Fix Code E95A

Step 1: Visual Inspection Begin by thoroughly inspecting the CAN bus wiring harness from the ECM (located near the engine) to the monitor controller in the cab. On used excavators, check for harness wear at known rub points, particularly where cables pass through the swing bearing area. Examine all connector terminals for corrosion, bent pins, or moisture intrusion.

Step 2: Electrical Testing Using a digital multimeter, verify proper termination resistance across the CAN-High and CAN-Low lines (should read approximately 60 ohms with both controllers connected). Check for voltage supply to both the ECM and monitor controller (typically 24V DC). Measure resistance between CAN-High and ground, then CAN-Low and ground—both should show high resistance (>10kΩ).

Step 3: Component Testing Connect Komatsu diagnostic software (KOMTRAX Plus or equivalent) to isolate which controller is failing to communicate. If one controller responds while the other doesn't, focus diagnostics on the non-responsive unit. Test termination resistors individually by disconnecting controllers and measuring resistance at harness ends.

Step 4: Repair and Verification Replace damaged harness sections or corroded connectors rather than attempting repairs on critical communication circuits. For used machines, apply dielectric grease to all reconnected terminals to prevent future corrosion. Clear the fault code and perform a complete operational test under load to verify proper communication restoration.

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Disclaimer: This guide provides general diagnostic information for Code E95A. Always consult the official Komatsu service manual for your specific machine serial number and consider professional diagnostic services for complex electrical issues. Improper repairs to control system wiring can cause additional damage or safety hazards.